2214 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
to form on the surface of pyrite. (Altun, 2010). Adsorption
of xanthate molecules primarily happens in conditions with
a mild degree of oxidation, where only minimal oxidation
of the mineral surface occurs. When the electric potential
increases, the oxidation products hinder or prevent the
transfer of electrons across the interface between the min-
eral and the solution. However, by employing a higher con-
centration of collectors, it is possible to achieve satisfactory
recovery even under higher potential conditions (Altun,
2010).
PYRITE ACTIVATION
Pyrite activation is a crucial process in the mineral process-
ing industry for separating and recovering valuable miner-
als from ore bodies (Ejtemaei &Nguyen, 2017b Peng et
al., 2012). It involves modifying the surface properties of
pyrite, primarily through surface chemistry alteration, to
increase its hydrophobicity (Peng et al., 2012). This modi-
fication allows pyrite to attach to air bubbles during flota-
tion, where surfactants called activators, such as copper or
lead ions, get adsorbed onto the pyrite surface to promote
collector adsorption (Ejtemaei &Nguyen, 2017a). Factors
affecting pyrite activation include pH, activator ion con-
centration, ore mineralogy, and the presence of other ions
in the flotation pulp (Nakhaei et al., 2023 Pecina et al.,
2006 Yang et al., 2022). Achieving selective activation of
pyrite without activating unwanted minerals is challenging,
and the environmental concerns and cost-effectiveness of
activators, especially heavy metals, must be considered.
Copper Sulfate
The adsorption of copper ion onto the pyrite surface is
firstly driven by the electrostatic attractions as pyrite sur-
face is negatively charged in a weakly acidic to alkali
medium while copper ions are positively charged (Yang
et al., 2021). The alterations in the surface chemistry of
pyrite upon interaction with copper ions play a crucial
role in hypothesizing the fundamental mechanisms of cop-
per activation. Ejtemaei and Nguyen (2017b) proposed a
two-step activation mechanism for pyrite using Cryogenic
X-ray Photoelectron Spectroscopy (Cryo-XPS), outlined as
follows:
• Reduction of copper ions (Cu2+ to Cu+): The initial
step in the copper activation of pyrite involves the
reduction of copper ions from a divalent state (Cu2+)
to a monovalent state (Cu+). This reduction is facili-
tated by the oxidation of sulfur species on the pyrite
surface. Specifically, the surface sulfide ions (S2–) are
oxidized to form a lower sulfur state (S–). This inter-
action indicates a charge transfer process, where the
pyrite surface acts as a reducing agent for the copper
ions (Ejtemaei &Nguyen, 2017b).
• Formation of a CuFeS2-type Layer: Following the
initial reduction of copper ions, there’s further
chemical interaction leading to the formation of a
CuFeS₂-type layer on the pyrite surface. This step
involves the oxidation of iron (Fe2+ to Fe3+) on the
pyrite surface, accompanied by the reduction of the
sulfur species (S– to S2–). The result is a layer that
resembles the mineral chalcopyrite (CuFeS₂), which
is known for its distinct and favorable flotation prop-
erties. The schematic in Figure 3 shows the copper
adsorption mechanism on pyrite mineral (Ejtemaei
&Nguyen, 2017b).
• Table 1 outlines the zeta potential measurements of
pyrite both before and after exposure to xanthate and
copper sulphate across a range of pH levels (Cheng
et al., 2020). Pyrite’s isoelectric point (IEP) was
found to occur around pH 4. Upon the addition of
xanthate, there was a significant decrease in pyrite’s
surface potential particularly at pH values below
7. Under highly acidic conditions, pyrite displayed
a positive surface charge, facilitating the adsorp-
tion of negatively charged xanthate anions onto its
surface (Yin et al., 2018). Conversely, in strongly
alkaline environments, pyrite underwent surface
oxidation and experienced intensified competitive
adsorption of OH– ions, resulting in the forma-
tion of Fe(OH)3. This hindered xanthate adsorp-
tion and reduced pyrite’s surface potential (Cheng
et al., 2020). Introduction of copper sulfate caused
an increase in the overall surface potential of pyrite,
attributed to the electrostatic adsorption of positively
charged Cu2+ or CuOH+ ions onto the pyrite surface
(Ejtemaei and Nguyen, 2017). As pH levels rose, the
abundance of positively charged ions diminished,
leading to a reversal in pyrite’s surface potential
towards negativity (Cheng et al., 2020).
The impact of pH on pyrite floatability was investigated
in the presence of copper sulfate by Nakhaei et al. (2023).
The results illustrated that in the presence of CuSO4 in the
slurry (at 50 g/t), pyrite recovery significantly decreases at
pH levels below 5, while exhibiting a marked increase at
pH levels above 7.5. Pyrite demonstrated depression in
the presence of CuSO4 at acidic pH levels and activation
only at alkaline pH levels. This phenomenon arises due to
the minimal adsorption of copper ions on the pyrite sur-
face at acidic pH, leading to a surplus of copper ions in
solution. These ions precipitate with the collector PAX
prior to adsorption, thereby reducing the available PAX
to form on the surface of pyrite. (Altun, 2010). Adsorption
of xanthate molecules primarily happens in conditions with
a mild degree of oxidation, where only minimal oxidation
of the mineral surface occurs. When the electric potential
increases, the oxidation products hinder or prevent the
transfer of electrons across the interface between the min-
eral and the solution. However, by employing a higher con-
centration of collectors, it is possible to achieve satisfactory
recovery even under higher potential conditions (Altun,
2010).
PYRITE ACTIVATION
Pyrite activation is a crucial process in the mineral process-
ing industry for separating and recovering valuable miner-
als from ore bodies (Ejtemaei &Nguyen, 2017b Peng et
al., 2012). It involves modifying the surface properties of
pyrite, primarily through surface chemistry alteration, to
increase its hydrophobicity (Peng et al., 2012). This modi-
fication allows pyrite to attach to air bubbles during flota-
tion, where surfactants called activators, such as copper or
lead ions, get adsorbed onto the pyrite surface to promote
collector adsorption (Ejtemaei &Nguyen, 2017a). Factors
affecting pyrite activation include pH, activator ion con-
centration, ore mineralogy, and the presence of other ions
in the flotation pulp (Nakhaei et al., 2023 Pecina et al.,
2006 Yang et al., 2022). Achieving selective activation of
pyrite without activating unwanted minerals is challenging,
and the environmental concerns and cost-effectiveness of
activators, especially heavy metals, must be considered.
Copper Sulfate
The adsorption of copper ion onto the pyrite surface is
firstly driven by the electrostatic attractions as pyrite sur-
face is negatively charged in a weakly acidic to alkali
medium while copper ions are positively charged (Yang
et al., 2021). The alterations in the surface chemistry of
pyrite upon interaction with copper ions play a crucial
role in hypothesizing the fundamental mechanisms of cop-
per activation. Ejtemaei and Nguyen (2017b) proposed a
two-step activation mechanism for pyrite using Cryogenic
X-ray Photoelectron Spectroscopy (Cryo-XPS), outlined as
follows:
• Reduction of copper ions (Cu2+ to Cu+): The initial
step in the copper activation of pyrite involves the
reduction of copper ions from a divalent state (Cu2+)
to a monovalent state (Cu+). This reduction is facili-
tated by the oxidation of sulfur species on the pyrite
surface. Specifically, the surface sulfide ions (S2–) are
oxidized to form a lower sulfur state (S–). This inter-
action indicates a charge transfer process, where the
pyrite surface acts as a reducing agent for the copper
ions (Ejtemaei &Nguyen, 2017b).
• Formation of a CuFeS2-type Layer: Following the
initial reduction of copper ions, there’s further
chemical interaction leading to the formation of a
CuFeS₂-type layer on the pyrite surface. This step
involves the oxidation of iron (Fe2+ to Fe3+) on the
pyrite surface, accompanied by the reduction of the
sulfur species (S– to S2–). The result is a layer that
resembles the mineral chalcopyrite (CuFeS₂), which
is known for its distinct and favorable flotation prop-
erties. The schematic in Figure 3 shows the copper
adsorption mechanism on pyrite mineral (Ejtemaei
&Nguyen, 2017b).
• Table 1 outlines the zeta potential measurements of
pyrite both before and after exposure to xanthate and
copper sulphate across a range of pH levels (Cheng
et al., 2020). Pyrite’s isoelectric point (IEP) was
found to occur around pH 4. Upon the addition of
xanthate, there was a significant decrease in pyrite’s
surface potential particularly at pH values below
7. Under highly acidic conditions, pyrite displayed
a positive surface charge, facilitating the adsorp-
tion of negatively charged xanthate anions onto its
surface (Yin et al., 2018). Conversely, in strongly
alkaline environments, pyrite underwent surface
oxidation and experienced intensified competitive
adsorption of OH– ions, resulting in the forma-
tion of Fe(OH)3. This hindered xanthate adsorp-
tion and reduced pyrite’s surface potential (Cheng
et al., 2020). Introduction of copper sulfate caused
an increase in the overall surface potential of pyrite,
attributed to the electrostatic adsorption of positively
charged Cu2+ or CuOH+ ions onto the pyrite surface
(Ejtemaei and Nguyen, 2017). As pH levels rose, the
abundance of positively charged ions diminished,
leading to a reversal in pyrite’s surface potential
towards negativity (Cheng et al., 2020).
The impact of pH on pyrite floatability was investigated
in the presence of copper sulfate by Nakhaei et al. (2023).
The results illustrated that in the presence of CuSO4 in the
slurry (at 50 g/t), pyrite recovery significantly decreases at
pH levels below 5, while exhibiting a marked increase at
pH levels above 7.5. Pyrite demonstrated depression in
the presence of CuSO4 at acidic pH levels and activation
only at alkaline pH levels. This phenomenon arises due to
the minimal adsorption of copper ions on the pyrite sur-
face at acidic pH, leading to a surplus of copper ions in
solution. These ions precipitate with the collector PAX
prior to adsorption, thereby reducing the available PAX